Raman spectroscopy is a label-free technique desired for biomolecular detections and molecular dynamic study. Surface enhanced Raman scattering (SERS) improves the sensitivity by amplifying the original Raman scattering intensity for several or even tens of orders of magnitude. Spherical gold and silver nanoparticles have been reported as substrates in SERS-based molecule detections due to their advantages in local scattering field enhancing, surface chemical modifications, biocompatibility, and well-established chemical synthesis process. The intrinsic plasmon resonance of single nanospheres and the plasmon coupling between adjacent nanospheres are considered as a key and necessary condition for local field enhancing. The optimal SERS substrate of spherical nanoparticle assemblies depends on the size, the local dielectric environment and the interparticle distance.
Surface-enhanced Raman scattering (SERS) spectroscopy shows chemical-bond information, and is one of the best methods for label-free biomolecular imaging. Conventional SERS substrates require multiple plasmonic couplings via many colloidal nanoparticles requiring particular coupling distances that are difficult to control in solution or biomolecular environments. In conventional chemical synthesis or batch fabrications, the interparticle distance is difficult to control due to the stochastic distribution of the nanospheres on a substrate.
The nanosphere is used because of its unique, highly desirable properties that make it a superior detection platform for life science research, in vitro diagnostic testing, and in vivo imaging. Other structures such as nanotips and nanorings have also been demonstrated for use in high resolution SERS spectroscopy and imaging. These structures provide significant field enhancement in experiments and in simulations but they have proved to be difficult to fabricate consistently. Although nanostructures for use in Raman Spectroscopy have been developed, there continues to be a need to develop nanostructures that have improved detect ability and ease of fabrication.